The invention relates to a crankcase ventilation system for an internal-combustion engine, having a main ventilating point arranged in a throttle valve housing and leading into the intake air flow in front of a throttle valve, with a secondary ventilating point arranged behind the throttle valve, and having a ventilating point arranged behind the throttle valve, and having a ventilating point arranged from the internal-combustion engine into a throttle valve housing with the throttle valve housing being connected to a coolant circulating system and being heated by it.
Crankcase ventilation systems are known, for example, from U.S. Pat. No. 3,364,910, in which a pipe leading out of the crankcase branches into two pipes which then lead to a main ventilating point located in front of a throttle valve and to a secondary ventilating point located behind the throttle valve. Therefore a total of three separate pipes are required in this case. An icing of both ventilating points, for example, as a result of freezing condensation water is not prevented. In the case of an icing, the crankcase can therefore not be ventilated. This is against the legal requirements and results in leaks, for example, at crankshaft sealing rings as a result of the resulting excess crankcase pressure.
A throttle valve, the icing of which is prevented by a ring duct through which cooling water flows and which extends in the throttle valve housing, is known from DE-PS No. 29 49 096.
It is an object of the present invention to provide a crankshaft ventilation system which, in a simple manner ventilates the crankcase into the air intake section during the normal load operation as well as in the coasting or idling operation of the internal-combustion engine, and in which an icing of the ventilating points in the air intake section is prevented.
According to the invention, this object is achieved by providing a system wherein the ventilating pipe inside the throttle valve housing branches into a duct leading to the main ventilating point and a duct leading to the secondary ventilating point.
The particular advantages of the invention are that the ventilating of the crankcase is achieved in all positions of the throttle valve in a simple manner, and that by arranging a ring duct through which the coolant flows in direct proximity of the throttle valve and the ventilating points, an icing of these points and of the throttle valve is prevented. In addition, only one line, which is usually constructed as a hose, is required for the feeding of the crankcase, and costs are reduced as well as the expenditures for the assembly and service. In addition, the throttle valve housing can be manufactured in one piece with all connections according to certain preferred embodiments.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings